Designing for Efficiency
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3. Loss Mechanisms in Switching Converters
Total converter loss is the sum of multiple interacting mechanisms:
Understanding each term clarifies how loss mechanisms arise in the switching stage and transformer of the reference
converter shown in Figure 1.
3.1 Conduction Losses
When a MOSFET conducts, current flows through its channel resistance:
Because resistance increases with temperature, conduction loss reinforces thermal rise. SiC devices maintain more stable
resistance at elevated temperature.
Diode conduction loss is approximated by:
Lower forward drop reduces dissipation.
3.2 Switching Losses
Switching loss occurs during voltage-current overlap:
Additional capacitance energy contributes:
Gate drive loss is:
These switching transitions occur in the primary push-pull stage of Figure 1 and are directly visible in the simulated switching
waveforms.
